The U.S. Post Office in Pearl River, New York, is located at the junction of Franklin and Main streets in the hamlet's downtown. It is a brick building from the mid-1930s, serving the ZIP Code 10965, which covers the hamlet of Pearl River. Its design, an application of the Colonial Revival architectural style commonly used for post offices of that era, is unique to it. It shows a strong modernist influence, with almost no ornament on its exterior, and no public art inside. In 1988 it was listed on the National Register of Historic Places with many other contemporary post offices in the state, including four others in Rockland County. Congress renamed the building the Heinz Ahlmeyer, Jr. Post Office Building in 2005, in honor of a local soldier missing in action and presumed dead during the Vietnam War until that year, when his remains were identified. Building The post office is located on the west side of Main Street, just south of its junction with Franklin Street on the east. It is oriented east-west, with its north (front) elevation facing the parking lot for the train station to its northwest. Across the parking lot to the north is Pearl River's town square; commercial buildings line its east side. The terrain slopes enough down to the railroad tracks to the west, exposing the post office's foundation on that side. On the other side of the tracks is a large industrial complex. The building itself is a one-story, five-by-five-bay steel frame structure with a concrete terrace surrounding the exposed basement portions of the foundation on the west. It consists of a three-bay central pavilion with two recessed one-bay wings on either side. A loading dock with canopy projects from the south into the postal vehicle parking lot. All three sections have a flat roof, with the central pavilion's slightly higher than the wings. They are faced in brick laid in common bond. A molded cast stone water table surrounds the building at floor level. Windows are 15-over-15 double-hung sash on the pavilion and eight-over-eight on the wings, with cast stone sills. The latter have recessed panels above them. Rooflines are marked by stone coping sheathed in aluminum. On the east facade, facing Main Street, a second entrance for employees was installed in a section with a slight projecting cast stone cornice. On the pavilion facade the windows rest on two cast